Three-dimensional carrier profiling of InP-based devices using scanning spreading resistance microscopy

Abstract

Scanning spreading resistance microscopy (SSRM) is a carrier profiling method based on atomic force microscopy (AFM), which has proven its power for two-dimensional semiconductor device analysis in the last few years. A three-dimensional approach is presented for depth profiling on the nm scale and for device inspection from the top surface. A procedure for SSRM on the InP structure is developed, where layers a few nm thick are continuously scratched away while scanning the region of interest with a highly doped diamond tip. This extends the SSRM to the third dimension, as SSRM images taken at different depths can be combined to construct a three-dimensional image of the sample. Based on the same technology, a “depth profiling” mode is developed whereby a well-defined etched pit is made. SSRM measurements taken on the side made of the etched pit provide a carrier profile to overcome the limitations of standard cross-sectional profiling and enable profiling of the layer with nm resolution.